My confusion about the Pegasus diagram is that there is no simple wire from the ignition switch to the coil in my car. My car has all sorts of fancy electronics, six ignition coils, an electronic anti-theft immobilizer, a multi-pole ignition switch with several wires on the output side, etc.

It's just not obvious what wire to disconnect to shut the car off. I was hoping that the simpler thing would in fact kill the engine, based on, among other things, this thread.